Control mechanism for a movable member



Sept. 4. 1956 H. ERICKSON Lowell H.. Erickson Fla-a Q20 @Yeni/yy MN, AL qgw ATTORNEYS Sept- 4, 1956 L. H. ERICKSON 2,761,323

CONTROL MECHANISM F'OR A MOVABLE MEMBER Filed Aug. 29, 1952 3 Sheets-Sheet. 2

INVENTOR. Lwell H. Erickson ATTORNEYS Spt 4, 1956 l.. H. ERxcKsoN 2,761,323

CONTROL MECHANISM FOR A MOVABLE MEMBER Filed Aug. 29, 1952 3 Sheets-Sheet 3 INVENTOR.

Lowell H. Erickson 47 'Fm-345 'WWMWKUM A TTOR N EYS CONTROL lVIECHANISM FOR A MOVABLE MEMBER Lowell H. Erickson, Denver, Colo., assigner to Marcellus S. Merrill, Denver, Colo.

Application August 29, 1952, Serial N 307,061 Claims. (Cl. 74-1415) This invention relates to control mechanism for a movable member and more particularly such a mechanism for easily moving a slidable member to any position in path of movement.

One of the objects of the invention is to produce improved control means operable by a single hand lever for moving a slidable member to any position in its path of movement from any other position.

Another object is to embody in said control means, structure which will insure that the slidable member will be held against sliding movement in any position to which it may be moved by the control means.

A further object is to produce 1improved means for moving a member which is mounted for sliding movement on parallel rails and which will embody structure cooperating with one of the rails to act as an abutment for a lever member cooper-able therewith and the member to bring about sliding movement thereof.

Yet another object is to produce improved mechanism for sliding a member on a support structure in either direction and for locking the member against movement when in any position to which it can be moved, said mechanism and its various functions all being controllable by a single hand operable member.

A further object is to produce improved means including ratchet means for moving in a step by step manner a member in opposite directions at will by a single handle which can cause the movement in one direction by an oscillatory movement at one side of a predetermined position and cause the movement in the opposite direction by an oscillatory movement at the opposite side of the predetermined position.

A still further object is to produce improved moving and locking means for a slidable member which will be controllable by a single hand operable lever and which permits locking to be accomplished by placing the lever in one position and will permit unlocking to be accomplished and moving to take place by placing the hand operable lever in a second position and then swinging it laterally away from and returning toward said second position, said swinging movement when taking place at one side of the second position causing step by step sliding movement of the movable member and when taking place at the other side of the second position causing step by step sliding movement of the movable member in the opposite direction.

Other objects of the invention will become apparent from the following description taken in connection with the accompanying drawings in which:

Figure 1 is a side view of a balancing machine in which is embodied structure, by way of example, embodying my invention, said view having parts broken away to show details of the construction;

Figure 2 is a bottom view of the moving and locking mechanism as viewed in the direction of the arrows on line 2 2 of Figure l;

Figure 3 is a sectional View of parts of the locking United States Patent 2,76 1,3213 PatentedA Sept.V 4,

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mechanism as viewed in the direction of the arrows ion the line 3-3 of Figure 1; Figure 4 is a view showing the single handle in its position when the locking mechanism is inoperative and the moving of the movable member can be accomplished, Figure 5 is a sectional view of the handle and itt connection to the locking rod and rotatable moving rod as viewed on the line 5-5 of Figure l; i

Figure 6 is a perspective view of one of the arms employed to lock onto a rail to act as an abutment in moving the slidable member; and l Figure 7 is a perspective View showing the locking shoe and the manner of its operation.

Referring to the drawings in detail and first to Figure 1, the structure embodying my invention is disclosed as being incorporated in a balancing machine where'itis useful to control the moving of a movable structure M positioned for sliding movement on a base B. The particular balancing machine shown also has another structure similar to the movable structure shown and this structure is fixed on the base B. It is by means of these two upstanding structures on the base B that there is supported on the balancing machine a vibratory cradle structure generally indicated by the letter C. Each structure M carries a cradle vibratableleaf spring 10 having one end fixed to a bracket 11 and its center resting upon a fulcrum 12 which can be moved to different positions by a threaded shaft 13 controllable by a handle 14. At the free end of the leaf spring 10 is a bearing structure 1S. The two bearing structures will provide supports upon which a rotatable body R can be placed and suitably rotated to observe conditions of unbalance so that proper corrective measures can be taken which are usually the adding of a weight or weights at certain points on the body. ln order to observe and determine the place and amount of unbalance of the body R, each vibratable leaf spring has associated therewith an Velectrical pickup P and these pickups are connected into an electronic hookup having associated therewith instruments for making the necessary observations and amount and place of the unbalance, this hookup not being shown as it forms no part of the present invention. The reason for moving the disclosed movable structure M is to so position the bearingsv 15 of the cradle relatively to each other that different lengths and sizes of bodies can be placed on the'cradle for balancing. To make the structure M movable, the base B has positioned on its top portion two parallel rails 16 and 17 and the bottom portion of the movable structure M is provided with suitable feet 1S and 19 for riding on the rails. It is, of course, desirable to provide simple control means for moving the structure M on the rails and further such control means that can be easily operated with a minimum of manual effort. The control means must further permit the member to be moved readilyV to any point along the rails and to do this the means 'should be capable of either causing very small movements or larger movements. Another feature which must be pro'- vided for the movable structure M is a locking means whereby the structure can be held at any desired position to which it has been moved on the rails so that when balancing operations are being performed, the movable structure M will have a rigid mounting on lthe base B and cannot shift when vibrations are being transmitted to the cradle by the rotating body R. For most eiicient operation, the control of both the moving and the holding of the movable structure M should be accomplished through the use of only one operable member. All'of these desirable conditions are obtained by my invention which is embodied in the structure now ,to`-be.des cribe d. The movable structure M at itsbottom isarrangecl to carry two similar parallel ratchet arms 20 and 21, al1

asllbest shown-in the-bottom view of Figure 2. The forwardendofthe vrann `20, also shown. in. Figure .6, is provided with a cross slot 22 of a width to receive the rail 16. This slot has special shaped side walls so that the `arm caneither .slide on the rail or .can Vhe .caused to grip the rail. As shown, opposed walls of the slot have por- ;tions 23 and 24V which are at right angles to the longitudinal .axis ofthe armand on opposite sides .of said axis. The slot valso has two parallel wall portions 25 and 26 whichare at au angle V.to the portions 23 and 24 and con- .tinuations thereof. With such a slot formation it is seen that if the arm 20 is moved in the direction of the .arrow shown in Figure 2 from the full line position to .thefdottedline position, it will be caused to grip the rail because of the portions 23 and 24 and their relationship laud-thus the arm can act as an abutment` When the arm is in the full line position shown in Figure 2, it will be inits normal condition where the arm can slide on 1therail'without any gripping action and during any slidling of the. arm itwill be impossible for the arm to grip the raiLdue-to the angular wallportions 25 and 26 of the slot.

The arm 21 is complementary Vto the arm 29 already .de scribed, lso it 'can be associated with the rail for either sliding or gripping action, the gripping action being accomplished when the arm is swung from its normal position in the direction of the arrow shown associated with the arm in Figure 2. The arm 21 has a slot 27 which receives the rail and this slot has the wall portions 28 and 29 vwhich are at right angles to the longitudinal axis of the arm and on opposite sides of the axis. There are also wall portions 30 and 31 which, as shown, are angu- .larly related to the portions 28 and 29.

The two arms extend from the rail 16 toward the iother rail 17 and between the free ends of the two arms there is positioned a lever 32 for selectively operating the arms. This lever is carried on the innerend of and actuated by a tubular operating shaft 33 which is journaled at its -innerend on a suitable support 34 is the base portion of thev movable structure M. The outer end of the shaft is journaled in an extending portion 35 ofthe movable structure M, which extension will also have mounted thereonthe-pickup P, all as shown in Figure l. The lever 32, ywhich is in the nature of a crank, carries on its free end, lwhich is vpositioned between the ratchet or gripping arms 20 and 21, a roller 36 in order to establish an anti- .friction engagement between the arms and the lever.

With this tubular shaft it will be seen that by a rotation thereof thelinovable structure M can be caused to be moved on the rails in either direction. I-f the shaft 33 rotated in the direction indicated by the X arrow of Figure 2, the lever 32 will cause the arm 20 to be swung inthedirection indicated by'the `arrow on said arm. This .swinging movement of the arm will result in the arm `gripping the rail v16 after Aa short swinging .movement and thus become an abutment on which the lever 32 can fulcrum. A continued rotation of the shaft after the varm 20grips the rail vwill result in the movement of the movablefstructure M on-the rails 16 and 17. in a direction laway from the arm 20 which has been caused to Ygrip the rail 16. The extent of movement of vthe .movable structure M will -be limited Vand may vary from any degree up to the .amount accomplished by greatest permissible swing -of the lever 32.

Knit-should be desired Vto move the movable structure M Aon the rails in a direction opposite to `that just described, the tubular shaft will vbe rotatedin the direction indicated .by the `Y arrow in vFigure 2. Such a rotation result in the arm 21 being Aacted upon .bythe lever 32 -.andcaused to so swing ythat it-will 'grip the yrail 16 l andestablish an abutment on vwhich the lever 32 can 'fulcrurn .Afterthe arm'21r grips vthe rail 16, any continued. rotation of the tubular shaft will result in the movement'of the movable Istructure M.

During any movement of the mov-able structure M, -the arm which is not acting as an abutment will move with the movable member and slide on the rail. In order that the arms may be normally held in their sliding position and always returned to such position when the lever is not operating on the arms, there is provided between the two arms coil springs 37 and 38, these springs being situated on the opposite sides of the rail 16. The ends of each coil spring extend into bores in each arm and are pinned in said bore. The ledge 46 and web 45 of the locking shoe act as spacers for the arms and any swinging movement of the arms will result rin tensioning and compressing of the springs. When neither arm is no longer being acted upon by the lever 32, the arms will assume their normal position as shown in full lines in Figure 2.

in order to lock the movable structure M in any position to which it may be moved on the rails 16 and 17, l associate with said rails a locking shoe L which is best shown in Figure 7. This locking shoe has two spaced side parts .39 and 40 connected together by integral bars, there being two end connecting bars 41 and 42 and two central connecting bars 43 and 44. Connecting the central bars is the integral web 4S. One end of the locking shoe carries a ledge 46 which is arranged to be positioned beneath the rail 16 and the other end of the locking shoe carries a ledge 47 which is arranged to be positioned beneath the rail 17. The ledge 46 and the web 45 of the locking shoe are of such width that they can be positioned between the two arms 20 and 21, but the other parts of the shoe are of a greater width since they will either be positioned above the arms 20'ar1d 21 or rearwardly of the free ends of said arms, all as shown in Figures 1 and 2.

With .such a locking shoe as described positioned in the structure shown so its ledges 46 and 47 are below the rails 16 and 17, it will he seen ythat if the shoe is Vraised upwardly, the ledges can be caused to engage the rails and thus clamp the movable structure M to the rails vand prevent any movement thereof. To control the lock- .ing shoe so it can be in locking or released position, there is connected to the top of web 45 a U-shaped member 48 by a bolt 49 screwed into the base part of the U-shaped member. The free ends of the y'el-shaped member lare provided with bearing openings Si? and 51 for receiving a shaft 52. This shaft has an eccentrically drilled bore 53 which receives a shaft 54 on which it can turn. Shaft 52 is supported at its ends in supports 55 and 56 suitably provided in the base portion of the movable structure M4 "Ehe shaft 52 carries an arm 57' which is secured to this shaft by a set screw 5S. The arm 57 extends downwardly between the legs of the U-shaped member 48 and is arranged to have its free end connected to a reciprocable shaft 59 by means of an L-shaped member 60. The L-shaped member has one end rotatably secured to the endof the rod 59 and its other end pivotally connected to the arm `5 7 by a pivot pin -61. The reciprocable rod is arranged to extend through the tubular shaft 33 which is employed to move the movable member in the manner valready described.

With this reciprocable rod and its connection with the locking shoe, vit is readily seen vthat the shoe can be fully controlled by the reciprocation thereof. With the vshoe ,and all the parts connected with lthe reciprocable .rod in the positions shown in Figure l, the shoe willbe engaged with the rails and thus the movable structure M will be held loolredto the rails. lf therecopricablerod 5S. vshould be moved to the right from the-position shown in .Figure l, the arm 57 and the shaft 52 will be given a clockwise rotation on the shaft S4. Since the shaft 5 2 is eccentricallyimounted on the shaft 54, the rotation of the arm 7 in the manner shown will result in the Uvshaped member` 48 being moved downwardly, carrying with it and releasing it from the rails and thereby permitting the movable structure M to be slidable ou the r ai1.s.

In accordance with one feature of my invention, I

control both the rotatable shaft 33 and the reciprocable rod 59 by a single control handle. This handle, designated as H, is shown in Figures 1, 4 and 5. The lower end of the handle has attached thereto a stirrup member 62. 'Ihe central part of this stirrup member is connected to the outer end or the reciprocable rod by a pivot pin 63. To the lower end of the stirrup member there is pivoted a crank 64 by means of a pivot pin 65. This crank is arranged to be carried on and secured to the outer end of the tubular shaft 33 where it extends through the extension portion 35 of the base part of the movable structure M. The connecting of the crank to the shaft is accomplished by a clamping action brought about by screws 66 operating on a split part of the hole of the crank which receives the shaft.

With the connection just described between the handle H and the reciprocable rod 59 and the rotatable tubular shaft 33, it is seen that the handle H can, by proper manipulation, selectively operate both the shaft and the rod. if rotation of the shaft is desired, the handle can be swung in the desired direction to accomplish the rotation. This movement of the handle will not have any effect whatsoever in reciprocating the rod 45. The rod. however, will be rotated and have free rotation with respect to the L-shaped connecting member 60 employed to connect the rod to the locking shoe. Rotating of the shaft 33 will only be done, however, after the locking shoe is released and this is accomplished by a swinging of the upper end of the handle outwardly away from the movable structure M; that is, from the straight up position shown in Figure l to the slanting position shown in Figure 4. Movement of the movable structure M to the left can only be accomplished by oscillating the handle to the left of its central position and movement of the movable structure M to the right can only be accomplished by oscillating the handle to the right of its central position. Thus, the operator will always know that when he desires to move the movable member in any direction, that direction will be determined by which side of the central position of the handle the oscillation is caused to take place.

From the foregoing description it will be seen that there is provided a very etiicient, simple and easily operable control mechanism for moving a movable member in either of two directions and for holding said movable member against movement wherever it may be positioned. All the functions of moving and holding are accomplished by the manipulation of a single handle in certain manners from a single predetermined position. The moving mechanism embodies a high leverage for moving any heavy member. Thus, there is no necessity for expending any great physical elort to accomplish the movement. When desired to move the movable structure M any great distances, the movement can be accomplished by a rapid oscillation of the handle on the proper side of its central position. With the oscillations there will be a step by step movement of the movable structure M each time that a ratchet arm or 21 is caused to grip the rail and act as an abutment so a step by step movement can be obtained. The ratchet arm,l upon return of the handle toward central position, will again assume the normal released position whereby it can be caused to grip the rail at a new position on the rail ahead of the point where it previously gripped.

Being aware of the possibility of modications in the particular structure discolsed as embodying my invention, all without departing from the fundamental principles of the invention, l desire it to be understood that the scope of the said invention is not to be limited in any manner except in accordance with the appended claims.

What is claimed is:

l. In control mechanism for a movable member, a fixed rail associated with the member and with respect to which the member is movable, an arm mounted on the member and having a portion cooperating with the rail for normal sliding movement thereon but capable of gripping the rail when swung in one direction, yieldable means holding the arm in normal position, a lever Acarried by the movable member and mounted to engage the arm and swing it to rail gripping position to thereby establish an abutment against which the lever can operate to move the movable member on the rail, a shaft journaled in the movable member with its axis in a plane parallel with the plane of movement of the arm, means connecting the shaft to swing the lever, and means for rotating the shaft and operating the lever.

2. ln control mechanism for a movable member, a xed rail associated with the member and with respect to which the member is movable, an arm mounted on the member and having a portion cooperating with the rail for normal sliding movement thereon but capable of gripping the rail when swung in one direction, a lever carried by the movable member and mounted to engage the arm and swing it to rail gripping position to thereby establish an 'abutment against which the lever can operate to move the movable member on the rail, a shaft operatively connected to said lever, means including a handle member operatively connected to said shaft for rotating the shaft and for moving the lever, and means operable by the movement of the handle member in a direction other than that required to rotate the shaft and move the lever for locking the movable member against movement.

3. In control mechanism for a movable member, a xed rail associated with the member and with respect to which the member is movable, two arms mounted in spaced relation on the member and each having a portion cooperating with the rail for normal sliding movement thereon, each of said portions being constructed and positioned for movement from a rail gripping position to a position permitting sliding movement thereof on said rail, said arms being capable of gripping the rail when swung in opposite direction, a lever carried by the movable member and mounted between the arms for selectively engaging one or the other of the arms to swing either to rail gripping position to thereby establish an abutment against which the lever can operate to positively move the movable member relatively to the rail in either direction, and by force transmitted through the lever and means for moving the lever to engage either arm and fulcrum thereon.

4. ln control mechanism for a movable member, a xed rail associated with the member and with respect to which the member is movable, two arms mounted in parallel relation on the member `and each having a portion c0- operating with the rail for normal sliding movement thereon, said arms being capable of gripping Athe rail when swung in opposite direction, Ia lever carried by the movable member and mounted between the arms to selectively engage the arms and swing either to rail gripping position to thereby establish `an abutment against which the lever can operate to move the movable member relatively to the rail in either direction, a locking member for engaging the rail and arranged to have a portion positioned between the arms, and means comprising a single operable member for selectively operating the lever and the locking member.

5. in control mechanism for a member mounted to slide on a support, means including a movable element carried by the member for engaging the support to thereby establish an abutment, means including lever means carried by the slidable member for acting on the first named means when it is engaging the support means for moving the slidable member, a manually operable member for operating the lever means, means including a movable locking member for engaging the support means to thereby hold the slidablemember from movement in either of two directions, and means controlled by a movement of the manually operable member in a direction other than that required to move the lever means for moving the locking member to operative and inoperative positions, said locking element being controllable independently of the slidable member.

6. In con-trol mechanism for a :member mounted to slide on a support, VVmeans carried by the member for engaging the support to thereby establish an abutment, means :including lever means carried by the slidable mem- .ber 4for actingfon the first named means .when it is engaging the support means for moving the slidable member, means including amovable vlocking member for engaging the support means to thereby hold the slidable member from movement, a tubular rotatable shaft for operating the lever means, a reciprocable rod extending through the shaft, a connection between the rod and the locking member for operating same, 'and means comprising a single operable member connected to the shaft and rod for selective operation thereof.

7. fln control 4mechanism for a member mounted to slide on a support, means carried by the member for engaging `the support lto thereby establish an abutment, means including 'lever meansvcarried by the slidable member .for acting on zthe :firstnamed Vmeans. when it is engaging the support ymear-.s for moving the slidable member, means .comprising a manually operable handle connected for operating the lever means by a swinging movement in one-direction, means including a movable locking member for engaging Ithe support means to thereby hold the slidable member from movement, and means controlled by a swinging movement of the handle in a `direction at substantial right angles to that required to move the lever means for moving the locking member to operative and inoperative positions, movable means operatively connested with said lever and with the locking member, said handle being operatively connected with said last named means.

8. In control mechanism for moving by manual force in opposite directions Va member mounted for slidable movement `on a support structure Aincluding a rail, spaced arms carried by the member and each constructed and mounted to slide yon the rail when in a normal position, said arms being arranged so that when one is swung away from the other it will grip the rail and thereby establish an abutment, a lever-carried by the member and positioned -betweenthe arms for selectively engaging one or the other ofthe arms and swinging the engaged arm to bring about a gripping of the rail and thus establish an .abutment so the .lever can act thereon and move the slidable member in .eitherfdirection depending on which arm is engaged `as an abutment, a rotatable shaft for moving the lever in opposite directions to Vthereby selectively act on the arms, and a handle for rotating the shaft.

' 9. ln -control mechanism for moving by manual force in `opposite directions a member mounted for slidable movement on a support structure including a rail, spaced arms .carried bythe member and each constructed with a slot Ato receive the rail and slide on the rail when in a normal position-extending vat right angles to the rail, said slot Aalso being constructedzso that when one arm is swung away `from the other it will .grip the rail and thereby establish an abutment, yieldable means holding the arms in vtheir normalsliding positionne lever carried by the memoer and positioned between the arms for selectively engaging and swinging one or -the other of the arms to bring about a gripping of the vrail and thus establish an abutment yso the lever can act thereon and move the slidable member in either direction depending on which arm is .engaged as an abutment, -andmeans for-moving the lever in opposite directions -to thereby selectively act on the arms.

l0. ln .control ,mechanismfor a member mounted for slidable movement-on asupport structure including a rail, spaced arms carried by the member and each constructed mounted 4toslide on therail when in a normal position, arms being arrangedso that when one .is swung away-from the other it will grip the rail and thereby establishanfabutmenh a lever carried by the member and posi- ,tioned 'betweengthe arms lto selectively engage and swing the arms to bring about :a gripping of the rail and thus establish an .abutment so the lever can act thereon and move the yslidable member, a rotatable shaft for moving the lever in opposite .directions to thereby selectively act on the arms, a handle for rotating the shaft, a reciprocable rod mounted in the shaft, a shoe carried by the slidable member and engageable with the rail to thereby lock the member to the rail, means for operating the shoe by the reciprocable rod, .and means for reciprocating the rod by a movement of the handle in a plane other than that employed to rotate the shaft.

ll. .ln control mechanism for a member mounted for slidable movement on .parallel rails, spaced arms carried by the member .and each constructed and mounted to slide on one rail when in a normal position, said arms being arranged so that when one is swung away from the other it will grip the rail and rthereby establish an abutment. a rotatable shaft carried by the slidable member, a lever on the end of the shaft and positioned between the arms to selectively engage and swing the arms to bring about a gripping of the rail and thus establish an abutment so the lever can act thereon and move the slidable member, a handle connected to the shaft for rotating the shaft by a swinging movement in one plane, said connecting Vof the handle .to the shaft permitting the handle to also swing in a direction at right angles to the plane ernployed to rotate the shaft, a reciprocable rod mounted in the shaft, a shoe carried by the slidable member and engageable with both rails to thereby lock the member to the rails, means for operating the shoe by the reciprocable rod, and means for reciprocating the rod by the movement of the handle in the right angle plane.

l2. ln control mechanism for a movable member, -a fixed rail associated with the member and with respect to which .the member is slida'ble, a rotatable shaft carried by ,the member, a handle for rotating the shaft, means comprising .ratchet arms carried by the slidable member in spaced relation forengaging and gripping the rail and thereby actas abutments, means including a lever operable by the shaft for selectively engaging one or the other of the arms to move them to gripping position and to then act thereon to move the movable member in opposite .directions by force transmitted from the lever, said lever :when engaging one arm only as an .abutment moving vthe movable .member in one direction and when engaging the other arm only as an abutment for moving the movable member in the opposite direction, said arms cach being mounted so as tofmove to a new gripping position each time the lever is oscillated to .be engaged with and disengaged from an arm.

13. Infcontrol mechanism for a member mounted for relative. slidable movement on a support structure including a rail, a rotatable shaft, a handle for rotating the shaft,

.and means carried by the slidable member and including -two ratchet elements for ratchet cooperation with the rail and operable by means associated with the shaft for step by step movingof the Vslidable member in opposite directions, said last named means including an additional element selectively engageable with oneior the other of said ratchet elements, one of the ratchet elements only of said last named means being operable to step by step move the slidable member in one direction when the handle is .oscillated at one side of a predetermined position and the other ratchet element only being operable to step by step more the slidable member in the opposite direction when the handle is oscillated at the otherside of the predetermined position.

14. in control mechanism for a member mounted for slidable movement on a support structure-including a rail, a rotatable shaft, a handle for rotating the shaft, means carried by the slidable member for ratchet cooperation with the rail and operable by the shaft for step by step movingfof the slidable member in opposite directions, said last named means being operable to step by step move the -slidable member in one direction when the handle is oscillated at one side of a predetermined position and operable to step by step move the slidable member in the opposite direction when the handle is oscillated at the other side of the predetermined position, means independent of the ratchet means for locking the movable member against sliding movement in either direction, and means connected to the locking means and operable by the handle when swung in a plane at right angles to its said planes of oscillation for controlling the operative and inoperative condition of the locking means.

15. A control mechanism for a movable structure associated With a fixed base structure, means including a single gripping member carried by the movable structure for gripping the base structure and establishing an abutment, means carried by the movable structure including a lever for operating the gripping member to gripping position and thereafter fulcruming on the said member for applying a force to move the movable structure on the base structure, means including a handle structure connected for operating the last named means, and locking means including ya locking element controllable by the handle structure for locking and unlocking the movable member to the base structure at will, said locking means being controllable independently of the gripping member.

References Cited in the le of this patent UNITED STATES PATENTS 1,091,160 Phillips Mar. 24, 1914 1,659,876 Jarvis Feb. 21, 1928 2,450,596 Kais Oct. 5, 1948 2,537,839 Lord Jan. 9, 1951 

